A United Nations program, at the crossroad between the development and the humanitarian mandate (UNISDR) turned the concept of resilience into a central vehicle for its worldwide program on disaster risk reduction. It is through an ethnographic study of the negotiation process, topped by interviews and text analyses that I suggest various characteristics to describe resilience in an international organization. With the perspective of the sociology of translation, I discuss, on the one hand, the UN's need to maintain a vague definition of the concept, which hinders operationalization and on the other, I show how the organization manages, with resilience, to legitimize its programs and sustainability.